The primary objectives of this research are to produce new data on prosodic aspects of speech after brain damage in patients who are native speakers of a tone language and, at the same time, address theoretical issues concerning the extent and nature of prosodic deficits in left brain-damaged aphasics, right brain-damaged nonaphasics, and cerebellar dysarthrics. The language selected for investigation is Thai, the national language of Thailand. A series of experimental phonetic investigations of fundamental frequency and timing in Thai are proposed to contribute original data that not only bear on specific theoretical issues concerning the underlying structure and processing of language in the human brain, but also serve to fill a conspicuous gap in acoustic phonetic information about fundamental frequency and timing beyond monosyllabic citation forms in normal speech. As a whole, this series of experiments is designed to show (1) that some elements of prosody may be impaired while others are spared following damage to the human brain; (2) that the size of the temporal domain over which prosodic features are manifested is the critical variable that determines their susceptibility to disruption; (3) that patients with right brain damage modulate speech prosody correctly in propositional speech, incorrectly in affective speech; and (4) that dysprosody in cerebellar dysarthria is qualitatively different from that in Broca's aphasia. The longer term objectives of this research program are (1) to provide a detailed, acoustical description of Fo and timing patterns in spontaneous and read speech of Thai-speaking patients with unilateral left and right hemisphere lesions, as well as other brain-damage patients with subcortical lesions, (2) to provide information on the perception abilities of these brain-damage patients with respect to linguistic contrasts in Thai mediated by Fo and timing, (3) to determine the relation between the production and perception abilities of these brain-damaged patients with respect to selected aspects of prosody in Thai, and 4) to show how both normal and abnormal Fo and timing patterns in tone language can give insight into the nature of language deficits that follow from damage to the brain.